Web winders are typically used to form large rolls of wound web material, such as paper and polymeric film materials, known as parent rolls. From the parent rolls, rewinders are employed in order to wind the web material into a rolled product. The rolled product is then cut at designated lengths into the finally wound product. Finally wound products typically created by these machines and processes are toilet tissue rolls, paper toweling rolls, paper rolls, polymeric films, and the like.
There are essentially two types of techniques known in the art for performing the step of rewinding, that is, winding a web material from a parent roll into a rolled product. The first technique used in winding a web material to form a rolled product is known as surface winding. In surface winding, the web material is wound onto the core via contact with belts and/or rotating rolls. A nip is typically formed between these two or more co-acting belt, or roller, systems. The belts or rollers of such systems typically travel in opposite directions at different speeds. The reason for having different speeds lies in the fact that the core that is being driven by the opposed belts or rollers will advance in the direction of the faster moving belt or roller. Usually these belts or rollers are divergent so that the rolled product that is being built upon the core will have enough space to grow in diameter, and will be able to maintain contact with the two diverging belts or rollers. Exemplary surface winders are disclosed in U.S. Pat. Nos. 3,630,462; 3,791,602; 4,541,583; 4,723,724; 4,828,195; 4,856,752; 4,909,452; 4,962,897; 5,104,155; 5,137,225; 5,226,611; 5,267,703; 5,285,979; 5,312,059; 5,368,252; 5,370,335; 5,402,960; 5,431,357; 5,505,405; 5,538,199; 5,542,622; 5,603,467; 5,769,352; 5,772,149; 5,779,180; 5,839,680; 5,845,867; 5,909,856; 5,979,818; 6,000,657; 6,056,229; 6,565,033; 6,595,458; 6,595,459; 6,648,266; 6,659,387; 6,698,681; 6,715,709; 6,729,572; 6,752,344; 6,752,345; and 6,866,220; the following International applications also provide exemplary surface winders; International Publication Nos. 01/16008 A1; 02/055420 A1; 03/074398 A2; 99/02439; 99/42393; and EPO Patent Application No. 0514226 A1.
However, such winders can have drawbacks. First, a typical surface winder provides significant contact between the web material and the winding surfaces during winding. This contact during winding can effectively translate winding torque through the web material leading to crushing of embossments that may be disposed upon an embossed material, smudging images disposed upon a web material having an image disposed thereon, and the like. Also, surface winders are known to exhibit winding log instability during the winding of low-density products.
The second technique used to wind a web material to form a rolled product is known as center winding. In center winding, a core is rotated in order to wind a web material into a roll around the core. Typically, this core is mounted on a mandrel that rotates at high speeds at the beginning of a winding cycle and then slows down as the size of the rolled product being wound upon the core increases in diameter. Center winders work well when the web material that is being wound has a printed, textured, or slippery surface. Additionally, center winders can be useful in producing softer rolled products. Exemplary center winders are discussed in U.S. Pat. Nos. 1,040,188; 2,769,600; 3,697,010; 4,588,138; 5,497,959; 5,660,349; 5,725,176; and U.S. Patent Application Publication No. 2002/0130212 A1.
However, center winders have drawbacks that are known to those of skill in the art. Known drawbacks include the need to provide a harder “pull” when rolling high-density and low-density web materials into a high-density roll. The resulting tension can provide for a Poisson lateral contraction of the web material, resulting in a non-uniformly wound product. Additionally, the application of tension to a perforated web material can cause the web material to rupture at a perforation during processing. This can cause a processing line to shut down.
It is clear that the prior art lacks a winder or rewinder capable of performing both center winding and surface winding in order to take advantage of the positive attributes that both processes enjoy. For example, it would be desirable to provide a winder that is capable of allowing a broader range of finished product roll densities. As will be appreciated by one of skill in the art, this capability, when coupled with known capabilities for imparting perforations at desired intervals and sheet counts in increments of one, can provide for a greatly enhanced product converting flexibility. This, in turn, can allow multiple finished product designs to be achieved using a common substrate. This is believed to provide substantial manufacturing expense savings by reducing changeovers on paper machines and converting lines, thereby avoiding multiple parent roll inventories, and the like. Such a desired hybrid winding system can also provide the capability to wind thick, highly embossed web materials into preferred high density finished product rolls having low sheet tension. As will soon be appreciated by one of skill in the art, this can improve product quality by eliminating sheet elongation and embossment distortion as well as improving winding reliability by providing fewer web material feed breaks in the winding process.